In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or a tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an infusion device for intravenous drug infusion, multiple vein punctures over a lengthy period would result in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an infusion system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent into an artery for diagnostic purposes. In other situations, there is a need to repetitively remove a body fluid for analysis from a remote body site. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and optical fibers are increasingly being utilized for monitoring body processes and could b more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or the withdrawal of body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements of the patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and represent a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir that can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an implanted catheter which communicates with a vein or other site within the patient where the infusion of therapeutic agents is desired. Implantation of such devices generally proceeds by making a small subcutaneous pocket in an appropriate area of the patient under local anesthesia. The implanted catheter is tunnelled to the desired infusion site. When the physician desires, to infuse or remove materials through the port, a hypodermic needle is used which pierces the skin over the infusion port and is placed into the port.
Although the presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing and since large diameter needles can seriously damage the septum, there are limitations in the diameter of needles which can be used to penetrate the septum. These diameter limitations severely restrict the opportunities provided by the port. In cases where it is desirable to infuse drugs using a flexible external catheter, the catheter must be fed through the needle that penetrates the septum. Such catheters have an extremely small inside diameter and, therefore, impose severe limitations on fluid flow rate and limit the types of fibers which can be introduced.
During prolonged infusions using a conventional port, the infusion needle is taped to the patient's skin to hold it in position. Conventional ports do not allow the needle to penetrate deeply into the port. Because of this, a small displacement of the needle can cause it to be pulled from the port. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which may require corrective surgery such as skin grafting or removal of tissue.
Presently available implantable drug infusion devices also have a significant size to provide an acceptable target surface area for the physician who must locate the port and penetrate the septum with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within the port or within the implanted catheter since it is difficult, if not impossible, to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal catheter. Present infusion ports also have a retained volume beneath the self-sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a physician desires to successively deliver multiple drugs to the same infusion site which are incompatible when mixed. Additionally, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports comprises an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the physician attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation which can cause significant undesirable consequences as mentioned above.
The present invention relates to a family of implantable infusion ports which provide numerous enhancements over prior art devices. In accordance with this invention, an infusion port is provided which incorporates the funnel-shaped entrance orifice which narrows down to a reduced diameter guide passageway. The guide passageway terminates at an internal cavity which retains an articulating catheter valve, such as a multi-element leaflet valve assembly. The port also has an exit passageway which is connected to an implanted catheter. This application describes numerous embodiments of alternative designs of patient access ports within the scope of the present invention.
In certain patient treatment applications there may be a need to provide an access port in which point of access is remote from the port valve. In prior embodiments of this invention, as described in the related applications, the patient access port has a housing which provides a valve chamber housing a valve which normally prevents the passage of fluids but which can be penetrated by an external flexible filament to permit access with the implanted catheter. In accordance with one aspect of the present invention, an access system is described in which an access housing is remote from the valve, and the components are connected by a flexible conduit. The implanted catheter is placed between the valve and the desired patient access site.
In prior embodiments of the present invention, various valving systems were described and claimed, including leaflet valves, ball valves, "flapper" type valves, etc. Each of these valve configurations is broadly encompassed by the description "articulating catheter valve" or "articulating valve", meaning that one or more valve elements are displaced in some predictable manner to provide access and which returns to an original position to provide a fluid seal. This type of valving scheme is distinguishable from those of the prior art which incorporate a compressed rubber septum which is repeatedly penetrated by a needle which leads to destruction and damage to the valving system. In accordance with one aspect of the present invention another valving configuration is described which is also considered an articulating valve. This alternative configuration valve is in the form of an elongated passageway formed of an elastomeric material which normally is maintained in a flattened occluded condition, but which can be penetrated by an external filament to cause it to open to provide access. Such a valve configuration can be incorporated within the housing of an access port or can be in the form of a tube attached to the outlet of an access housing.
In certain patient therapeutic applications there is a need to simultaneously infuse two incompatible materials or withdraw fluid from one site while infusing to another. One example of such application is in hemodialysis in which blood is drawn from a peripheral vein, treated, and thereafter returned to the patient. In such applications, a pair of access routes is required. In accordance with one aspect of the present invention, an access port is provided which has two separate and distinct access passageways defined by separate entrance orifices, valves and outlets, all incorporated into a single housing. This "dual port" can be connected to separate and distinct implanted catheters, or to a dual lumen catheter. In order to provide the clinician with an indication of the differences between intended functions of the two access pod entrance orifices external indicating features can be formed on the access housing which can be palpated by the clinician.
As a means of facilitating the use of implanted access pods, there is a continuing need to facilitate the implantation process in a manner which minimizes trauma to the patient and simplifies the implantation procedure. In accordance with an aspect of this invention, an infusion pod is provided having a housing shaped to facilitate its insertion through a narrow incision placed in the patient, for example, in the forearm area. By providing the housing with a tapered "dart" configuration, an incision having a width narrower than the cross-sectional width of the pod can be used. The port housing is inserted through the narrow incision causing the skin to be slightly stretched around the incision area during port placement which causes the skin upon returning to its unstretched condition to aid in retaining the port in position. This invention also involves a special surgical tool which forms a slit in the skin and a subcutaneous pocket which is shaped to fit to accommodate an implanted access port.
Access ports in accordance with the prior disclosed embodiments of this invention have been described as being formed of a hard material such as stainless steel, titanium or other metals. Although the use of hard materials such as a metal or ceramic is needed in the entrance orifice area where a sharp instrument such as a needle or trocar would be used to access the device, resistance to damage by a sharp instrument is generally not required in other portions of the access port. As a means of increasing design flexibility and perhaps reducing cost of production of access ports, another aspect of this invention is to form a composite port, made from several materials. A hard material would be used to form the inside surface of the entrance orifice which would guide any sharp accessing instrument to the entrance orifice focus area and thereafter into an internal passageway. Another material, for example, a moldable polymeric material, could be used to form the remainder of the port. The described composite pod further features a smoothly bent passageway which acts as a "needle stop" which is believed to provide advantages over prior embodiments in which the. passageway has an abrupt change in direction.
In previous embodiments of access ports in accordance with this invention, the access port is used to access a single site within the patient. There are however, potential applications where there may be a need to access several sites using a single access port. Accordingly, the present invention contemplates access systems in which a "bifurcated" flow path is provided. In accordance with this invention, a pair of valves are paced in series with a branching flow path between the valves. Access to one site is provided by penetrating only one valve, by penetrating both valves, the second site is accessed. Another embodiment of a bifurcated flow system involves use of a branched implanted catheter where the flow path is defined through the use of a steerable guidewire or catheter having a bent end which is directed into one of the plural branching pathways.
In embodiments of access ports previously described in the related applications, the mechanism for causing the articulating valve to open is direct engagement between an external filament and a valve element. Other types of valve actuation approaches are possible which may be advantageous in certain port applications. In accordance with this invention, several embodiments of access ports are described in which the valve mechanism is directly actuated through external palpation and thus opening of the valve does not depend solely upon direct contact between the external filament and a valve element.
In some of the previous designs of access devices in accordance with this invention which are designed to be accessed using a sharp instrument such as a needle or trocar which is used to introduce a flexible filament, there is a feature referred to as a "needle stop" in the port entrance passageway which prevents the needle from contacting and possibly damaging the valve element. In the prior embodiments such a needle stop is provided by the passageway having a change in direction which a rigid element cannot negotiate between the entrance orifice and the valve. In accordance with another aspect of the present invention, an alternate scheme for a needle stop is provided in the form of a passageway having a decreasing inside diameter. When a needle is used to access the device and the flexible external filament is fed through the inside of the needle, the needle is stopped as the passageway diameter decreases to less than the outside diameter of the needle.
Various accessing approaches are possible using the access ports in accordance with the present invention including conventional needles, sharp trocars, blunt instruments, and catheter-over-needle combinations such as the "Anglocath".TM.. Yet another aspect of this invention is another access instrument which combines the skin penetration capabilities of a sharpened metal object with the flexibility of an external filament. Several embodiments of composite accessing filaments are described herein in which a flexible or semi-flexible catheter is used having a sharpened hard end surface for skin penetration. These devices, also referred to as "self-introducing catheters" would be used with access ports with a port valve designed to interact with the sharpened tip without unacceptable damage and wear.
Still another aspect of this invention is a simplified means of locating the entrance orifice of an access port after implantation. Such features are provided through the use of a template which is placed over the implanted access port and provide an indication to the clinician as to the position and orientation of the inlet orifice, thus simplifying the process of locating the target area of the access port.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.